Gene Expression Flashcards
Nucleic acid definitions
group of chemicals in the cells that control our genetic information.
What are the two types of nucleic acids
- DNA (Deoxyribo Nucleic Acid)
- RNA (RiboNucleic Acid)
Both DNA and RNA are made up of monomers(building blocks) called….
nucleotides
The double stranded DNA molecule is large and consists of thousands of….
genes.
The order of bases along the DNA molecule forms the information called the….
Genetic Code.
Template strand of DNA- is used to form….
the mRNA to carry information for protein synthesis.
Non-template or coding strand- is….
the other strand of DNA (not involved in forming the mRNA).
has the same base sequence as the mRNA except U replaces T on mRNA.
Non-template / coding strand
mRNA definition
formed inside the nucleus from the template strand of DNA (transcription).
- carries the information to the ribosome to make protein.
tRNA definition
is located in the cytoplasm
- brings specific amino acids to the ribosome
rRNA definition
forms structure of the ribosome (this is where proteins are made).
triplet definition
sequence of 3 bases on the template strand of DNA.
codon definition
sequence of 3 bases on the mRNA.
Anticodon definition
sequence of 3 bases on the tRNA.
- Inside the nucleus
- Deoxyribose sugar
- Adenine,Thymine,Guanine,
Cytosine bases - Larger (upto several billion nucleotides)
- Has 2 strands (double helix shape)
- Longer lifespan
DNA
- located In the cytoplasm
- Ribose sugar
- Adenine,Uracil,Cytosine, Guanine bases
- Smaller (upto 20,000 nucleotides)
Single stranded - Shorter lifespan
RNA
Genetic code is the name given to ….
all the hereditary information in the DNA.
There are 4 bases to code….
for the 20 amino acids, therefore produces 64 different combinations if 3 letter codes are used.
Degeneracy means the genetic code is set up….
so that more than one codon codes for the same amino acid.
The advantage of redundancy due to degeneracy is….
that if a mutation occurs in the 3rd base ,it might not cause a change in the amino acid coded for.
- therefore lessens the effect of mutation on an individual. therefore structure and function of protein remains unchanged.
AUG is….
a start codon that signals the start site of translation
UAA, UAG, and UGA are….
stop codons that signal the end of translation, and have no amino acids associated with them.
How many amino acids in our body?
20 amino acids
Protein synthesis definition
the process where proteins are made by using the mRNA
What process of protein synthesis occurs first?
Transcription then translation.
Describe the process of transcription (4 steps)
- For transcription to occur….
- The start codon on the template strand of….
- The enzyme RNA Polymerase forms
- Once the mRNA is formed it….
- For transcription to occur, the DNA molecule is unwound at a particular gene.
- The start codon on the template strand of DNA signals the beginning of transcription and the stop codon signals the ending of transcription.
- The enzyme RNA Polymerase forms the mRNA by using the template strand of DNA. The base-pairing rule is used to form the strand of mRNA(A-T and C-G but Thymine is replaced by Uracil on the mRNA).
- Once the mRNA is formed, it undergoes editing and then it leaves the nucleus and attaches to the ribosome in the cytoplasm where translation occurs.
What is transcription and where does it occur?
Process of forming mRNA using the template strand of DNA.
It occurs inside the nucleus.
What is translation and where does it occur?
Is where the code sequence carried on the mRNA is used to create a functional protein.
Occurs at the ribosome in the cytoplasm.
Describe the process of translation
(5 steps)
- The ribosome reads….
- The start codon (AUG) that…..
- The tRNA (UAC) will bring….
- The next codons will…
- The polypeptide chain is….
- The ribosome reads the codons on the mRNA and these have a complementary anti-codon on the tRNA.
- The Start codon(AUG) that codes for amino acid Met; on the mRNA will be the signal for the beginning of translation.
- The tRNA(UAC) will bring the Met amino acid to where the mRNA is joined to the ribosome.
- The next codons will then be matched with their anti-codons on tRNA. Specific amino acids are brought by the tRNA and the amino acids are joined by the peptide bonds until the Stop codon is reached. This signals the end of the synthesis of the protein chain.
- The polypeptide chain is released from the ribosome and ‘folds’ into a three-dimensional structure, becoming a functional protein.
Mutation definition
a permanent change to the base sequence of the DNA
What are the three mutation effects
- Nonsense mutation
- Missense mutation
- Silent mutation
Nonsense mutation
mutation that causes an early stop codon
Missense mutation
a mutation that changes a codon to that of a different amino acid
Silent mutation
a mutation that causes no change to amino acid
What are the two types of mutations
- Frameshift mutation (deletion or insertion)
- Point mutation
Frameshift mutation definition
Causes the reading after mutation to be all incorrect or cause an early stop
Point mutation definition
One base change (Could be a substitution=swap, could be an insertion/del of one base)
Base substitution definition
A base is exchanged/replaced with another.
Base substitution effect
- May alter amino acid
- Results in a new amino acid being coded for, so new protein is slightly different, causing it to be less effective, or non-functional. (a base substitution not at the first or second base will result in a different amino acid in the enzyme).
- Results in early termination where shortened protein is non-functional because a STOP codon is coded for at the earlier end of mRNA.
- Results in the same amino acid being coded for, due to redundancy of the genetic code. (only if the base is substituted at the 3rd position of a triplet).
Base deletion definition
Involves deletion of a base/s to the base sequence.
Effect of base deletion
- Results in reading frame shift, where new sequences of triplets are read, resulting in new amino acid sequences so the new protein has different properties, and is likely to be non-functional.
- Results in early termination, where shortened protein is non-functional.
Base insertion definition
Involves addition of a base/s to the base sequence.
Effect of base insertion
- Results in reading frame shift, where new sequences of triplets are read, resulting in new amino acid sequences so the new protein has different properties, and is likely to be non-functional.
- Results in early termination, where shortened protein is non-functional.
Mutagen definition
factors that increase the mutation rate
What are two examples of mutagens
UV light.
Chemicals
How does chemicals act as a mutagen
The chemicals react with specific nucleotide bases in the DNA & change its composition
Name three example of chemicals that act as mutagens
- Mustard gas
- Formaldehyde
- Agent orange
A metabolic pathway is…..
a series of enzyme controlled steps (linked biochemical reactions), where specific enzymes control each step.
When there is a mutation in a gene in a metabolic pathway….
you can get differences in the phenotype of an organism as the pathway stops in an intermediate position.
Genotype definition
Refers to the two alleles a person inherits for a particular gene
Phenotype definition
Physical expression of the genotype
What aspects of the external environment affect an organisms genetic potential (3)
- Starvation or malnutrition
- Lack of light
- Temperature
How does starvation or malnutrition affect genetic potential
can affect the proper development of both plants and animals.
How does lack of light affect genetic potential
can prevent formation of chlorophyll or development in seedlings. Light also affects skin colour.
How does temperature affect genetic potential
can affect enzyme systems.
How internal environment affect genetic potential
One gene can affect another
All of the genes in an organism’s body determine its…
genetic potential, or what it might be.
What actually happens, depends on the internal and external environment.
Internal environmental factors include….
an organism’s sex, age and the presence of other genes which may switch off or modify a particular gene.
External environmental factors include……
temperature, light, wind, moisture level, nutrition, chemicals and human influence. These factors affect an organism during its embryonic development or after it is born.
